Apparatus for roasting zinc ores



Oct. 10, 1933. A. L. J. QUENEAU APPARATUS FOR ROASTING ZINC ORES 4 Sheets-Sheet 1 m a a mfi 4 w w 3 a Q a m 3 k 0 K/ L I m 6 s N 3 W. A a n g 9 A J\ l I l 1| B I 1933- A. L. J. QUENEAU 1,929,713

APPARATUS FOR ROASTING ZINC ORBS Original Filed Out. 25, 1929 4 Sheets-Sheet s 7 BY filo ATTORNEYS 1933- A. J. QUENEAU APPARATUS FUR RCA STING ZINC ORE'S 4 Sheets-Sheet 4 Original Filed Oot'. 25 1929 ill???iii/$2,- 4,855 .iiihih YINVENTOR 01 14917521171 Zea/z (190/2 file/lead BY- .KM ATTORNEYS Patented Oct. 10, 1933 APPARATUS FOR ROASTING ZINC ORES Augustin Leon Jean Queneau, New York, N. Y.

Original application 402,418. Divided and tober 25, 1929, Serial No. this application October 30, 1930., Serial No. 492,340

6 Claims.

This invention relates to improved apparatus for the treatment of sulphide ores. While not limited thereto the invention is particularly well suited for the treatment of zinc bearing materials. In the prior application, Serial No. 402,-

418, filed October 25, 1929, I have disclosed an improved method and apparatus for roasting zinc. This application is a division of said prior application and is directed particularly to the improved apparatus.

- In the usual roasting operation, the heat liberation is extremely rapid at the beginning of the roast where there is abundant sulphur and on the other hand is extremely slow toward the end of the roast where there is a deficiency of sulphur available. Thus, in the prior practice, there was an excessive heat liberation at the begimiing and a deficiency at the end of the roast. It has heretofore been proposed to introduce green ore (unroasted ore) at different points in the furnace.

In one known type of furnace (the McDougall shelf-roaster) and in subsequent modifications thereof, the ore to be roasted is caused to circulate progressively from shelves by means of a suitable mechanical device having a number of rabbling arms. In this former type of roaster means have been provided for feeding the green ore to the lower hearths and the activity of oxidation has been increased and it has been almost possible to secure the so-called dead roast without the use of extraneous fuel. The operation may be said to be an autogenous roasting. In the well known type of furnace heretofore used, zinc'ore has been roasted down to approximately 4% to 4 of residual sulphur without the use of additional carbonaceous fuel.

One object of the present invention is to secure substantially the same result, but by a different and more efficient means hereinafter described, moreover, the invention applies particularly to the dead roasting of sulphide ores in such a manner that sulphuric acid can be recovered economically from the outgoing gas products.

The invention will be fully apparent from the following specification when read in connection Fig. 4 is an enlarged detail on line 4-4 of Fig. 2;

Fig. 5 is a vertical section on line 5-5 of Fig. 4.

Referring in detail to. the drawings, 10 represents a sulphur roasting furnace having a plurality of superposed shelves 12 over which the ore fed from the hopper 14 travels progressively from top to bottom, the same being propelled by air cooled rabbling armslfi carried by a hollow central shaft 18 driven by suitable motor driven mechanism indicated at 20.

I provide a steel vessel indicated at 22 which has a steam coil 24 for maintaining in molten condition a body of sulphur, indicated at 26. This sulphur is adapted to be led through suitable steam jacketed pipes indicated at 28 to a plurality of sulphur burners. indicated at, 30. Each pipe 28 will be provided with a valve 32 by means of which the quantity of liquid sulphur fed to the burner can be varied manually so as to secure a fine degree of adjustment.

Each burner 30 is enclosed in a chamber 'structure 34 secured to the outer shell of the roaster. As best shown in Figs. 4 and 5, each burner 30 includes a plurality of superposed pans 36, each having legs 38 on which they are supported in proper relationship. Each pan is provided with an apertured lug 40 forming an overflow port so as to maintain levels of sulphur at points indicated at 42 in Fig. 4. With this arrangement, it is impossible for the molten sulphur from the several pans 36 to overflow or to in any way come into detrimental contact with the ore being treated, on the hearth of the roaster. 36 empties into a catch basin 44 having anoutlet 46, which in turn empties into a pipe 48 leading to any suitable .vessel outside of the roaster.

,For supporting combustion of the molten sulphur supplied to the several pans 36 of the burners 30, I provide means for introducing heated air to the chamber members 34 which inclose the burner pans.

As best shown in Figs. 1 to 3 air is supplied under pressure by a suitable fan or blower 50 through a pipe 51 to the hollow shaft 18, this air serving to cool the shaft and the several rabbling arms 16. A portion of the air is discharged through nozzles 19 into the furnace. The remainder of the air in passing through the shaft 18 and rabbling arms is preheated and a certain proportion thereof .is passed through an air regulating valve 52 to a down-comer pipe The overflow 40 of the lowermost pan 54. This pipe is provided with a flow meter 56 and a regulating valve 58 by means of which the operator can accurately supply the requisite amount of air to take care of the combustion needs of the furnace and so as to maintain a proper proportion of air and sulphur.

Branch pipes 56 lead from the lower portion of the pipe 54 th the several burners. Each branch pipe is equipped with a regulating valve 58 and a gauge 60 by means of which the operator can accurately determine and maintain the pressure of air supplied. A high grade zinc sulphide oi'e usually contains approximately 30% of sulphur, thus, by adding green ore as heretofore done in the zone where there is usually a deficiency of heat, former'operators add only 30% by weight of the ore addition as the sulphur fuel.

In my improved apparatus instead of addin the sulphur fuel in the form of sulphide ore in a solid state, I add 100% sulphur fuel by weight. I am enabled to do this by introducing brimstone or pure sulphur and heated air.

Sulphur at ordinary temperatures is a solid. It usually occurs in lump form and it is rather difiicult to obtain in a fine state of division such as would be required for close regulation of quantities such as would be accurately introduced at various points of a roasting furnace.

To overcome this difficulty, I melt the sulphur and introduce the resulting liquid through suitable steam jacketed pipes to different parts of the roasting furnace. The supply of liquid sulphur to any desired part of the roasting furnace is controlled by a simple stop-cock, as above described.

Sulphur melts at a low temperature (about 116.5 C.) and this temperature can readily be reached by the use of steam at approximately a pressure of 100 pounds at a temperature of 164? C.

In dead roasting zinc ore it is necessary to raise the temperature on the last hearth to about 900 C. and above in order to break up the residual zinc sulphate'which dissociates at 767 C. but in order to obtain complete and rapid dissociation in the ore bed a temperature of 900v C. is a necessity. To obtain this high temperature it has been necessary heretofore to use exclusively for dead'roasting some form of carbonaceous fuel or hydrocarbon. If the roast gases are to be used for acid manufacture the amount of fuel used, outside of other economic considerations, is to be restricted, and in any event the H20 and CO2 contents of the products of combustion interfere with the efficiency of the acid plant. It is the usual practice to burn this type of fuel in so-called muflle chambers out of contact with the ore under'treatment, the products of combustion being released to the atmosphere. The heat'of combustion is conducted to ore under treatment by conduction through the refractory walls.

It is to avoid the use of carbonaceous or hydrocarbon fuels with the resulting disadvantages that I use brimstone sulphur. However, to obtain a satisfactory utilization of its calorific power it is preferable to burn it under the specifled conditions herein disclosed.

In the practice, I admit preheated air at say 250 0., preferably higher, this air being taken conveniently from the air used to cool the shaft and rabble arms of the roasting furnace and I limit the amount of air so as to have almost perfect combustion with 15% or better S02 in the products of combustion leaving the sulphur burner. The temperature of combustion under this strictly controlled method of combustion is theoretically 1225 C. and making due allowance for all heat losses, the .temperature level of practically 900 C. or 1000 C. is attained.

For good practice, I have determined that in order to secure a dead roast of zinc ore there is a consumption of from 10% to 12% of sulphur brimstone burned as fuel for each ton of green ore treated. That is to say, for each ton of green ore I burn approximately 200 to 240 pounds of brimstone sulphur fuel.

In order to maintain the most eflicient roasting conditions, preheated air is preferably supplied under pressure to the several sulphur burners in such carefully regulated quantities with relation to the amount of sulphur fuel supplied to the burners so as to maintain a temperature of not less than 900 C. on the lowest hearth. Under these conditions the products of combustion leaving the burner will include from 10% to 15% or more $02.

In Fig. 1, I have indicated that the molten sulphur is fed by gravity to the uppermost pan of the burner and the rate of flow thereto is controlled accurately by a valve. The valve permits the operator to accurately control the amount of sulphur fed in accordance with the amount of air supplied to the burner so as to maintain proper operating conditions. An important feature of the invention resides in accurately maintaining a predetermined proportion between the amount of fuel and the amount'of air supplied to the furnace whereby an almost perfect combustion of sulphur is secured so that the products of combustion leaving the burner contain preferably not less than 10% S02.

The maintenance of these conditions enables me to hold the temperature in the lower part of the apparatus between 900 to 1000" C.

The foregoing description and the accompanying illustrations disclose a preferred embodiment of the invention. It is not to be construed, however, that I am limited to such specific construction since various modifications and substitution of equivalents may be made by those skilled in the art without departure from the invention as defined in the appended claims.

While I have described quite specifically certain relative amounts of sulphurous fuel and certain preferred temperatures it is to be understood that such speciflc examples are to be interpreted in an illustrative rather than a limiting sense.

What I claim is: 7,

1. In combination, an ore roasting furnace, a burner directly communicating with a lower portion of said furnace, said burner including .at least one pan adapted to hold a body of liquid sulphur, means to continuously supply liquid sulphur to said pan, means to supply a regulable quantity of air to said burner, and means to preheat said air before entering said burner by advancing said air through a conduit in said furnace.

2. In combination, a vessel adapted to maintain a body of sulphur in a molten condition, a sulphur burner including a plurality of superposed pans, means to convey the molten sulphur from the vessel to said pans, means to pass a regulable volume of air over said pans, and means to preheat said air.

3. In combination, an ore roasting furnace of the multiple hearth type, a sulphur burner disposed exteriorly .to said furnace, said burner comprising a plurality of burner pans, means to feed molten sulphur to said pans, means to supply preheated air to said burner, and means to conduct the hot sulphur dioxide gases from the sulphur burner directly into said furnace without substantial loss in sensible heat energy at a point where they will circulate over the lower hearth of said furnace.

4. In a sulphide ore roasting furnace means to conduit sulphur dioxide containing gases directly over the substantially oxidized ore, and means externally connected with the body of said furnace to produce said gases, said means comprising a sulphur burner including means in combination therewith to maintain the sulphur in a molten condition, means to supply the molten sulphur to the burner in regulated amounts, means to pass controlled amounts of air preheated by said furnace over said molten sulphur in the burner and means to conduct the products of combustion from the burner directly into the roasting furnace, without substantial loss of absorbed heat energy.

5. An ore roasting furnace comprising a plurality of superposed hearths, means to supply ore to the uppermost hearth, means to feed said ore successively to each lower hearth, means to supply an oxidizing blast to the interior of said furnace, and means to introduce heated sulphur dioxide containing gases within the furnace at a point where said gases will circulate over the ore upon the lower hearth of said furnace.

6. In apparatus of the type described and claimed in claim 5, means to introduce heated sulphur dioxide gases into the furnace includ: ing a sulphur burner exhausting into the furtrace and means for preheating the air for said burner.

' AUGUSTIN LEON JEAN QUENEAU. 

